1// SPDX-License-Identifier: GPL-2.0
2#include <linux/slab.h>
3#include <linux/file.h>
4#include <linux/fdtable.h>
5#include <linux/freezer.h>
6#include <linux/mm.h>
7#include <linux/stat.h>
8#include <linux/fcntl.h>
9#include <linux/swap.h>
10#include <linux/ctype.h>
11#include <linux/string.h>
12#include <linux/init.h>
13#include <linux/pagemap.h>
14#include <linux/perf_event.h>
15#include <linux/highmem.h>
16#include <linux/spinlock.h>
17#include <linux/key.h>
18#include <linux/personality.h>
19#include <linux/binfmts.h>
20#include <linux/coredump.h>
21#include <linux/sort.h>
22#include <linux/sched/coredump.h>
23#include <linux/sched/signal.h>
24#include <linux/sched/task_stack.h>
25#include <linux/utsname.h>
26#include <linux/pid_namespace.h>
27#include <linux/module.h>
28#include <linux/namei.h>
29#include <linux/mount.h>
30#include <linux/security.h>
31#include <linux/syscalls.h>
32#include <linux/tsacct_kern.h>
33#include <linux/cn_proc.h>
34#include <linux/audit.h>
35#include <linux/kmod.h>
36#include <linux/fsnotify.h>
37#include <linux/fs_struct.h>
38#include <linux/pipe_fs_i.h>
39#include <linux/oom.h>
40#include <linux/compat.h>
41#include <linux/fs.h>
42#include <linux/path.h>
43#include <linux/timekeeping.h>
44#include <linux/sysctl.h>
45#include <linux/elf.h>
46#include <linux/pidfs.h>
47#include <linux/net.h>
48#include <linux/socket.h>
49#include <net/af_unix.h>
50#include <net/net_namespace.h>
51#include <net/sock.h>
52#include <uapi/linux/pidfd.h>
53#include <uapi/linux/un.h>
54#include <uapi/linux/coredump.h>
55
56#include <linux/uaccess.h>
57#include <asm/mmu_context.h>
58#include <asm/tlb.h>
59#include <asm/exec.h>
60
61#include <trace/events/task.h>
62#include "internal.h"
63
64#include <trace/events/sched.h>
65
66static bool dump_vma_snapshot(struct coredump_params *cprm);
67static void free_vma_snapshot(struct coredump_params *cprm);
68
69#define CORE_FILE_NOTE_SIZE_DEFAULT (4*1024*1024)
70/* Define a reasonable max cap */
71#define CORE_FILE_NOTE_SIZE_MAX (16*1024*1024)
72/*
73 * File descriptor number for the pidfd for the thread-group leader of
74 * the coredumping task installed into the usermode helper's file
75 * descriptor table.
76 */
77#define COREDUMP_PIDFD_NUMBER 3
78
79static int core_uses_pid;
80static unsigned int core_pipe_limit;
81static unsigned int core_sort_vma;
82static char core_pattern[CORENAME_MAX_SIZE] = "core";
83static int core_name_size = CORENAME_MAX_SIZE;
84unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT;
85static atomic_t core_pipe_count = ATOMIC_INIT(0);
86
87enum coredump_type_t {
88 COREDUMP_FILE = 1,
89 COREDUMP_PIPE = 2,
90 COREDUMP_SOCK = 3,
91 COREDUMP_SOCK_REQ = 4,
92};
93
94struct core_name {
95 char *corename;
96 int used, size;
97 unsigned int core_pipe_limit;
98 bool core_dumped;
99 enum coredump_type_t core_type;
100 u64 mask;
101};
102
103static int expand_corename(struct core_name *cn, int size)
104{
105 char *corename;
106
107 size = kmalloc_size_roundup(size);
108 corename = krealloc(cn->corename, size, GFP_KERNEL);
109
110 if (!corename)
111 return -ENOMEM;
112
113 if (size > core_name_size) /* racy but harmless */
114 core_name_size = size;
115
116 cn->size = size;
117 cn->corename = corename;
118 return 0;
119}
120
121static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
122 va_list arg)
123{
124 int free, need;
125 va_list arg_copy;
126
127again:
128 free = cn->size - cn->used;
129
130 va_copy(arg_copy, arg);
131 need = vsnprintf(buf: cn->corename + cn->used, size: free, fmt, args: arg_copy);
132 va_end(arg_copy);
133
134 if (need < free) {
135 cn->used += need;
136 return 0;
137 }
138
139 if (!expand_corename(cn, size: cn->size + need - free + 1))
140 goto again;
141
142 return -ENOMEM;
143}
144
145static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
146{
147 va_list arg;
148 int ret;
149
150 va_start(arg, fmt);
151 ret = cn_vprintf(cn, fmt, arg);
152 va_end(arg);
153
154 return ret;
155}
156
157static __printf(2, 3)
158int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
159{
160 int cur = cn->used;
161 va_list arg;
162 int ret;
163
164 va_start(arg, fmt);
165 ret = cn_vprintf(cn, fmt, arg);
166 va_end(arg);
167
168 if (ret == 0) {
169 /*
170 * Ensure that this coredump name component can't cause the
171 * resulting corefile path to consist of a ".." or ".".
172 */
173 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
174 (cn->used - cur == 2 && cn->corename[cur] == '.'
175 && cn->corename[cur+1] == '.'))
176 cn->corename[cur] = '!';
177
178 /*
179 * Empty names are fishy and could be used to create a "//" in a
180 * corefile name, causing the coredump to happen one directory
181 * level too high. Enforce that all components of the core
182 * pattern are at least one character long.
183 */
184 if (cn->used == cur)
185 ret = cn_printf(cn, fmt: "!");
186 }
187
188 for (; cur < cn->used; ++cur) {
189 if (cn->corename[cur] == '/')
190 cn->corename[cur] = '!';
191 }
192 return ret;
193}
194
195static int cn_print_exe_file(struct core_name *cn, bool name_only)
196{
197 struct file *exe_file;
198 char *pathbuf, *path, *ptr;
199 int ret;
200
201 exe_file = get_mm_exe_file(current->mm);
202 if (!exe_file)
203 return cn_esc_printf(cn, fmt: "%s (path unknown)", current->comm);
204
205 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
206 if (!pathbuf) {
207 ret = -ENOMEM;
208 goto put_exe_file;
209 }
210
211 path = file_path(exe_file, pathbuf, PATH_MAX);
212 if (IS_ERR(ptr: path)) {
213 ret = PTR_ERR(ptr: path);
214 goto free_buf;
215 }
216
217 if (name_only) {
218 ptr = strrchr(path, '/');
219 if (ptr)
220 path = ptr + 1;
221 }
222 ret = cn_esc_printf(cn, fmt: "%s", path);
223
224free_buf:
225 kfree(objp: pathbuf);
226put_exe_file:
227 fput(exe_file);
228 return ret;
229}
230
231/*
232 * coredump_parse will inspect the pattern parameter, and output a name
233 * into corename, which must have space for at least CORENAME_MAX_SIZE
234 * bytes plus one byte for the zero terminator.
235 */
236static bool coredump_parse(struct core_name *cn, struct coredump_params *cprm,
237 size_t **argv, int *argc)
238{
239 const struct cred *cred = current_cred();
240 const char *pat_ptr = core_pattern;
241 bool was_space = false;
242 int pid_in_pattern = 0;
243 int err = 0;
244
245 cn->mask = COREDUMP_KERNEL;
246 if (core_pipe_limit)
247 cn->mask |= COREDUMP_WAIT;
248 cn->used = 0;
249 cn->corename = NULL;
250 cn->core_pipe_limit = 0;
251 cn->core_dumped = false;
252 if (*pat_ptr == '|')
253 cn->core_type = COREDUMP_PIPE;
254 else if (*pat_ptr == '@')
255 cn->core_type = COREDUMP_SOCK;
256 else
257 cn->core_type = COREDUMP_FILE;
258 if (expand_corename(cn, size: core_name_size))
259 return false;
260 cn->corename[0] = '\0';
261
262 switch (cn->core_type) {
263 case COREDUMP_PIPE: {
264 int argvs = sizeof(core_pattern) / 2;
265 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
266 if (!(*argv))
267 return false;
268 (*argv)[(*argc)++] = 0;
269 ++pat_ptr;
270 if (!(*pat_ptr))
271 return false;
272 break;
273 }
274 case COREDUMP_SOCK: {
275 /* skip the @ */
276 pat_ptr++;
277 if (!(*pat_ptr))
278 return false;
279 if (*pat_ptr == '@') {
280 pat_ptr++;
281 if (!(*pat_ptr))
282 return false;
283
284 cn->core_type = COREDUMP_SOCK_REQ;
285 }
286
287 err = cn_printf(cn, fmt: "%s", pat_ptr);
288 if (err)
289 return false;
290
291 /* Require absolute paths. */
292 if (cn->corename[0] != '/')
293 return false;
294
295 /*
296 * Ensure we can uses spaces to indicate additional
297 * parameters in the future.
298 */
299 if (strchr(cn->corename, ' ')) {
300 coredump_report_failure("Coredump socket may not %s contain spaces", cn->corename);
301 return false;
302 }
303
304 /* Must not contain ".." in the path. */
305 if (name_contains_dotdot(name: cn->corename)) {
306 coredump_report_failure("Coredump socket may not %s contain '..' spaces", cn->corename);
307 return false;
308 }
309
310 if (strlen(cn->corename) >= UNIX_PATH_MAX) {
311 coredump_report_failure("Coredump socket path %s too long", cn->corename);
312 return false;
313 }
314
315 /*
316 * Currently no need to parse any other options.
317 * Relevant information can be retrieved from the peer
318 * pidfd retrievable via SO_PEERPIDFD by the receiver or
319 * via /proc/<pid>, using the SO_PEERPIDFD to guard
320 * against pid recycling when opening /proc/<pid>.
321 */
322 return true;
323 }
324 case COREDUMP_FILE:
325 break;
326 default:
327 WARN_ON_ONCE(true);
328 return false;
329 }
330
331 /* Repeat as long as we have more pattern to process and more output
332 space */
333 while (*pat_ptr) {
334 /*
335 * Split on spaces before doing template expansion so that
336 * %e and %E don't get split if they have spaces in them
337 */
338 if (cn->core_type == COREDUMP_PIPE) {
339 if (isspace(*pat_ptr)) {
340 if (cn->used != 0)
341 was_space = true;
342 pat_ptr++;
343 continue;
344 } else if (was_space) {
345 was_space = false;
346 err = cn_printf(cn, fmt: "%c", '\0');
347 if (err)
348 return false;
349 (*argv)[(*argc)++] = cn->used;
350 }
351 }
352 if (*pat_ptr != '%') {
353 err = cn_printf(cn, fmt: "%c", *pat_ptr++);
354 } else {
355 switch (*++pat_ptr) {
356 /* single % at the end, drop that */
357 case 0:
358 goto out;
359 /* Double percent, output one percent */
360 case '%':
361 err = cn_printf(cn, fmt: "%c", '%');
362 break;
363 /* pid */
364 case 'p':
365 pid_in_pattern = 1;
366 err = cn_printf(cn, fmt: "%d",
367 task_tgid_vnr(current));
368 break;
369 /* global pid */
370 case 'P':
371 err = cn_printf(cn, fmt: "%d",
372 task_tgid_nr(current));
373 break;
374 case 'i':
375 err = cn_printf(cn, fmt: "%d",
376 task_pid_vnr(current));
377 break;
378 case 'I':
379 err = cn_printf(cn, fmt: "%d",
380 task_pid_nr(current));
381 break;
382 /* uid */
383 case 'u':
384 err = cn_printf(cn, fmt: "%u",
385 from_kuid(to: &init_user_ns,
386 kuid: cred->uid));
387 break;
388 /* gid */
389 case 'g':
390 err = cn_printf(cn, fmt: "%u",
391 from_kgid(to: &init_user_ns,
392 kgid: cred->gid));
393 break;
394 case 'd':
395 err = cn_printf(cn, fmt: "%d",
396 __get_dumpable(mm_flags: cprm->mm_flags));
397 break;
398 /* signal that caused the coredump */
399 case 's':
400 err = cn_printf(cn, fmt: "%d",
401 cprm->siginfo->si_signo);
402 break;
403 /* UNIX time of coredump */
404 case 't': {
405 time64_t time;
406
407 time = ktime_get_real_seconds();
408 err = cn_printf(cn, fmt: "%lld", time);
409 break;
410 }
411 /* hostname */
412 case 'h':
413 down_read(sem: &uts_sem);
414 err = cn_esc_printf(cn, fmt: "%s",
415 utsname()->nodename);
416 up_read(sem: &uts_sem);
417 break;
418 /* executable, could be changed by prctl PR_SET_NAME etc */
419 case 'e':
420 err = cn_esc_printf(cn, fmt: "%s", current->comm);
421 break;
422 /* file name of executable */
423 case 'f':
424 err = cn_print_exe_file(cn, name_only: true);
425 break;
426 case 'E':
427 err = cn_print_exe_file(cn, name_only: false);
428 break;
429 /* core limit size */
430 case 'c':
431 err = cn_printf(cn, fmt: "%lu",
432 rlimit(RLIMIT_CORE));
433 break;
434 /* CPU the task ran on */
435 case 'C':
436 err = cn_printf(cn, fmt: "%d", cprm->cpu);
437 break;
438 /* pidfd number */
439 case 'F': {
440 /*
441 * Installing a pidfd only makes sense if
442 * we actually spawn a usermode helper.
443 */
444 if (cn->core_type != COREDUMP_PIPE)
445 break;
446
447 /*
448 * Note that we'll install a pidfd for the
449 * thread-group leader. We know that task
450 * linkage hasn't been removed yet and even if
451 * this @current isn't the actual thread-group
452 * leader we know that the thread-group leader
453 * cannot be reaped until @current has exited.
454 */
455 cprm->pid = task_tgid(current);
456 err = cn_printf(cn, fmt: "%d", COREDUMP_PIDFD_NUMBER);
457 break;
458 }
459 default:
460 break;
461 }
462 ++pat_ptr;
463 }
464
465 if (err)
466 return false;
467 }
468
469out:
470 /* Backward compatibility with core_uses_pid:
471 *
472 * If core_pattern does not include a %p (as is the default)
473 * and core_uses_pid is set, then .%pid will be appended to
474 * the filename. Do not do this for piped commands. */
475 if (cn->core_type == COREDUMP_FILE && !pid_in_pattern && core_uses_pid)
476 return cn_printf(cn, fmt: ".%d", task_tgid_vnr(current)) == 0;
477
478 return true;
479}
480
481static int zap_process(struct signal_struct *signal, int exit_code)
482{
483 struct task_struct *t;
484 int nr = 0;
485
486 signal->flags = SIGNAL_GROUP_EXIT;
487 signal->group_exit_code = exit_code;
488 signal->group_stop_count = 0;
489
490 __for_each_thread(signal, t) {
491 task_clear_jobctl_pending(task: t, JOBCTL_PENDING_MASK);
492 if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
493 sigaddset(set: &t->pending.signal, SIGKILL);
494 signal_wake_up(t, fatal: 1);
495 nr++;
496 }
497 }
498
499 return nr;
500}
501
502static int zap_threads(struct task_struct *tsk,
503 struct core_state *core_state, int exit_code)
504{
505 struct signal_struct *signal = tsk->signal;
506 int nr = -EAGAIN;
507
508 spin_lock_irq(lock: &tsk->sighand->siglock);
509 if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
510 /* Allow SIGKILL, see prepare_signal() */
511 signal->core_state = core_state;
512 nr = zap_process(signal, exit_code);
513 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
514 tsk->flags |= PF_DUMPCORE;
515 atomic_set(v: &core_state->nr_threads, i: nr);
516 }
517 spin_unlock_irq(lock: &tsk->sighand->siglock);
518 return nr;
519}
520
521static int coredump_wait(int exit_code, struct core_state *core_state)
522{
523 struct task_struct *tsk = current;
524 int core_waiters = -EBUSY;
525
526 init_completion(x: &core_state->startup);
527 core_state->dumper.task = tsk;
528 core_state->dumper.next = NULL;
529
530 core_waiters = zap_threads(tsk, core_state, exit_code);
531 if (core_waiters > 0) {
532 struct core_thread *ptr;
533
534 wait_for_completion_state(x: &core_state->startup,
535 TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
536 /*
537 * Wait for all the threads to become inactive, so that
538 * all the thread context (extended register state, like
539 * fpu etc) gets copied to the memory.
540 */
541 ptr = core_state->dumper.next;
542 while (ptr != NULL) {
543 wait_task_inactive(ptr->task, TASK_ANY);
544 ptr = ptr->next;
545 }
546 }
547
548 return core_waiters;
549}
550
551static void coredump_finish(bool core_dumped)
552{
553 struct core_thread *curr, *next;
554 struct task_struct *task;
555
556 spin_lock_irq(lock: &current->sighand->siglock);
557 if (core_dumped && !__fatal_signal_pending(current))
558 current->signal->group_exit_code |= 0x80;
559 next = current->signal->core_state->dumper.next;
560 current->signal->core_state = NULL;
561 spin_unlock_irq(lock: &current->sighand->siglock);
562
563 while ((curr = next) != NULL) {
564 next = curr->next;
565 task = curr->task;
566 /*
567 * see coredump_task_exit(), curr->task must not see
568 * ->task == NULL before we read ->next.
569 */
570 smp_mb();
571 curr->task = NULL;
572 wake_up_process(tsk: task);
573 }
574}
575
576static bool dump_interrupted(void)
577{
578 /*
579 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
580 * can do try_to_freeze() and check __fatal_signal_pending(),
581 * but then we need to teach dump_write() to restart and clear
582 * TIF_SIGPENDING.
583 */
584 return fatal_signal_pending(current) || freezing(current);
585}
586
587static void wait_for_dump_helpers(struct file *file)
588{
589 struct pipe_inode_info *pipe = file->private_data;
590
591 pipe_lock(pipe);
592 pipe->readers++;
593 pipe->writers--;
594 wake_up_interruptible_sync(&pipe->rd_wait);
595 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
596 pipe_unlock(pipe);
597
598 /*
599 * We actually want wait_event_freezable() but then we need
600 * to clear TIF_SIGPENDING and improve dump_interrupted().
601 */
602 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
603
604 pipe_lock(pipe);
605 pipe->readers--;
606 pipe->writers++;
607 pipe_unlock(pipe);
608}
609
610/*
611 * umh_coredump_setup
612 * helper function to customize the process used
613 * to collect the core in userspace. Specifically
614 * it sets up a pipe and installs it as fd 0 (stdin)
615 * for the process. Returns 0 on success, or
616 * PTR_ERR on failure.
617 * Note that it also sets the core limit to 1. This
618 * is a special value that we use to trap recursive
619 * core dumps
620 */
621static int umh_coredump_setup(struct subprocess_info *info, struct cred *new)
622{
623 struct file *files[2];
624 struct coredump_params *cp = (struct coredump_params *)info->data;
625 int err;
626
627 if (cp->pid) {
628 struct file *pidfs_file __free(fput) = NULL;
629
630 pidfs_file = pidfs_alloc_file(pid: cp->pid, flags: 0);
631 if (IS_ERR(ptr: pidfs_file))
632 return PTR_ERR(ptr: pidfs_file);
633
634 pidfs_coredump(cprm: cp);
635
636 /*
637 * Usermode helpers are childen of either
638 * system_dfl_wq or of kthreadd. So we know that
639 * we're starting off with a clean file descriptor
640 * table. So we should always be able to use
641 * COREDUMP_PIDFD_NUMBER as our file descriptor value.
642 */
643 err = replace_fd(COREDUMP_PIDFD_NUMBER, file: pidfs_file, flags: 0);
644 if (err < 0)
645 return err;
646 }
647
648 err = create_pipe_files(files, 0);
649 if (err)
650 return err;
651
652 cp->file = files[1];
653
654 err = replace_fd(fd: 0, file: files[0], flags: 0);
655 fput(files[0]);
656 if (err < 0)
657 return err;
658
659 /* and disallow core files too */
660 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
661
662 return 0;
663}
664
665#ifdef CONFIG_UNIX
666static bool coredump_sock_connect(struct core_name *cn, struct coredump_params *cprm)
667{
668 struct file *file __free(fput) = NULL;
669 struct sockaddr_un addr = {
670 .sun_family = AF_UNIX,
671 };
672 ssize_t addr_len;
673 int retval;
674 struct socket *socket;
675
676 addr_len = strscpy(addr.sun_path, cn->corename);
677 if (addr_len < 0)
678 return false;
679 addr_len += offsetof(struct sockaddr_un, sun_path) + 1;
680
681 /*
682 * It is possible that the userspace process which is supposed
683 * to handle the coredump and is listening on the AF_UNIX socket
684 * coredumps. Userspace should just mark itself non dumpable.
685 */
686
687 retval = sock_create_kern(net: &init_net, AF_UNIX, type: SOCK_STREAM, proto: 0, res: &socket);
688 if (retval < 0)
689 return false;
690
691 file = sock_alloc_file(sock: socket, flags: 0, NULL);
692 if (IS_ERR(ptr: file))
693 return false;
694
695 /*
696 * Set the thread-group leader pid which is used for the peer
697 * credentials during connect() below. Then immediately register
698 * it in pidfs...
699 */
700 cprm->pid = task_tgid(current);
701 retval = pidfs_register_pid(pid: cprm->pid);
702 if (retval)
703 return false;
704
705 /*
706 * ... and set the coredump information so userspace has it
707 * available after connect()...
708 */
709 pidfs_coredump(cprm);
710
711 retval = kernel_connect(sock: socket, addr: (struct sockaddr *)(&addr), addrlen: addr_len,
712 O_NONBLOCK | SOCK_COREDUMP);
713
714 if (retval) {
715 if (retval == -EAGAIN)
716 coredump_report_failure("Coredump socket %s receive queue full", addr.sun_path);
717 else
718 coredump_report_failure("Coredump socket connection %s failed %d", addr.sun_path, retval);
719 return false;
720 }
721
722 /* ... and validate that @sk_peer_pid matches @cprm.pid. */
723 if (WARN_ON_ONCE(unix_peer(socket->sk)->sk_peer_pid != cprm->pid))
724 return false;
725
726 cprm->limit = RLIM_INFINITY;
727 cprm->file = no_free_ptr(file);
728
729 return true;
730}
731
732static inline bool coredump_sock_recv(struct file *file, struct coredump_ack *ack, size_t size, int flags)
733{
734 struct msghdr msg = {};
735 struct kvec iov = { .iov_base = ack, .iov_len = size };
736 ssize_t ret;
737
738 memset(s: ack, c: 0, n: size);
739 ret = kernel_recvmsg(sock: sock_from_file(file), msg: &msg, vec: &iov, num: 1, len: size, flags);
740 return ret == size;
741}
742
743static inline bool coredump_sock_send(struct file *file, struct coredump_req *req)
744{
745 struct msghdr msg = { .msg_flags = MSG_NOSIGNAL };
746 struct kvec iov = { .iov_base = req, .iov_len = sizeof(*req) };
747 ssize_t ret;
748
749 ret = kernel_sendmsg(sock: sock_from_file(file), msg: &msg, vec: &iov, num: 1, len: sizeof(*req));
750 return ret == sizeof(*req);
751}
752
753static_assert(sizeof(enum coredump_mark) == sizeof(__u32));
754
755static inline bool coredump_sock_mark(struct file *file, enum coredump_mark mark)
756{
757 struct msghdr msg = { .msg_flags = MSG_NOSIGNAL };
758 struct kvec iov = { .iov_base = &mark, .iov_len = sizeof(mark) };
759 ssize_t ret;
760
761 ret = kernel_sendmsg(sock: sock_from_file(file), msg: &msg, vec: &iov, num: 1, len: sizeof(mark));
762 return ret == sizeof(mark);
763}
764
765static inline void coredump_sock_wait(struct file *file)
766{
767 ssize_t n;
768
769 /*
770 * We use a simple read to wait for the coredump processing to
771 * finish. Either the socket is closed or we get sent unexpected
772 * data. In both cases, we're done.
773 */
774 n = __kernel_read(file, buf: &(char){ 0 }, count: 1, NULL);
775 if (n > 0)
776 coredump_report_failure("Coredump socket had unexpected data");
777 else if (n < 0)
778 coredump_report_failure("Coredump socket failed");
779}
780
781static inline void coredump_sock_shutdown(struct file *file)
782{
783 struct socket *socket;
784
785 socket = sock_from_file(file);
786 if (!socket)
787 return;
788
789 /* Let userspace know we're done processing the coredump. */
790 kernel_sock_shutdown(sock: socket, how: SHUT_WR);
791}
792
793static bool coredump_sock_request(struct core_name *cn, struct coredump_params *cprm)
794{
795 struct coredump_req req = {
796 .size = sizeof(struct coredump_req),
797 .mask = COREDUMP_KERNEL | COREDUMP_USERSPACE |
798 COREDUMP_REJECT | COREDUMP_WAIT,
799 .size_ack = sizeof(struct coredump_ack),
800 };
801 struct coredump_ack ack = {};
802 ssize_t usize;
803
804 if (cn->core_type != COREDUMP_SOCK_REQ)
805 return true;
806
807 /* Let userspace know what we support. */
808 if (!coredump_sock_send(file: cprm->file, req: &req))
809 return false;
810
811 /* Peek the size of the coredump_ack. */
812 if (!coredump_sock_recv(file: cprm->file, ack: &ack, size: sizeof(ack.size),
813 MSG_PEEK | MSG_WAITALL))
814 return false;
815
816 /* Refuse unknown coredump_ack sizes. */
817 usize = ack.size;
818 if (usize < COREDUMP_ACK_SIZE_VER0) {
819 coredump_sock_mark(file: cprm->file, mark: COREDUMP_MARK_MINSIZE);
820 return false;
821 }
822
823 if (usize > sizeof(ack)) {
824 coredump_sock_mark(file: cprm->file, mark: COREDUMP_MARK_MAXSIZE);
825 return false;
826 }
827
828 /* Now retrieve the coredump_ack. */
829 if (!coredump_sock_recv(file: cprm->file, ack: &ack, size: usize, MSG_WAITALL))
830 return false;
831 if (ack.size != usize)
832 return false;
833
834 /* Refuse unknown coredump_ack flags. */
835 if (ack.mask & ~req.mask) {
836 coredump_sock_mark(file: cprm->file, mark: COREDUMP_MARK_UNSUPPORTED);
837 return false;
838 }
839
840 /* Refuse mutually exclusive options. */
841 if (hweight64(ack.mask & (COREDUMP_USERSPACE | COREDUMP_KERNEL |
842 COREDUMP_REJECT)) != 1) {
843 coredump_sock_mark(file: cprm->file, mark: COREDUMP_MARK_CONFLICTING);
844 return false;
845 }
846
847 if (ack.spare) {
848 coredump_sock_mark(file: cprm->file, mark: COREDUMP_MARK_UNSUPPORTED);
849 return false;
850 }
851
852 cn->mask = ack.mask;
853 return coredump_sock_mark(file: cprm->file, mark: COREDUMP_MARK_REQACK);
854}
855
856static bool coredump_socket(struct core_name *cn, struct coredump_params *cprm)
857{
858 if (!coredump_sock_connect(cn, cprm))
859 return false;
860
861 return coredump_sock_request(cn, cprm);
862}
863#else
864static inline void coredump_sock_wait(struct file *file) { }
865static inline void coredump_sock_shutdown(struct file *file) { }
866static inline bool coredump_socket(struct core_name *cn, struct coredump_params *cprm) { return false; }
867#endif
868
869/* cprm->mm_flags contains a stable snapshot of dumpability flags. */
870static inline bool coredump_force_suid_safe(const struct coredump_params *cprm)
871{
872 /* Require nonrelative corefile path and be extra careful. */
873 return __get_dumpable(mm_flags: cprm->mm_flags) == SUID_DUMP_ROOT;
874}
875
876static bool coredump_file(struct core_name *cn, struct coredump_params *cprm,
877 const struct linux_binfmt *binfmt)
878{
879 struct mnt_idmap *idmap;
880 struct inode *inode;
881 struct file *file __free(fput) = NULL;
882 int open_flags = O_CREAT | O_WRONLY | O_NOFOLLOW | O_LARGEFILE | O_EXCL;
883
884 if (cprm->limit < binfmt->min_coredump)
885 return false;
886
887 if (coredump_force_suid_safe(cprm) && cn->corename[0] != '/') {
888 coredump_report_failure("this process can only dump core to a fully qualified path, skipping core dump");
889 return false;
890 }
891
892 /*
893 * Unlink the file if it exists unless this is a SUID
894 * binary - in that case, we're running around with root
895 * privs and don't want to unlink another user's coredump.
896 */
897 if (!coredump_force_suid_safe(cprm)) {
898 /*
899 * If it doesn't exist, that's fine. If there's some
900 * other problem, we'll catch it at the filp_open().
901 */
902 do_unlinkat(AT_FDCWD, name: getname_kernel(cn->corename));
903 }
904
905 /*
906 * There is a race between unlinking and creating the
907 * file, but if that causes an EEXIST here, that's
908 * fine - another process raced with us while creating
909 * the corefile, and the other process won. To userspace,
910 * what matters is that at least one of the two processes
911 * writes its coredump successfully, not which one.
912 */
913 if (coredump_force_suid_safe(cprm)) {
914 /*
915 * Using user namespaces, normal user tasks can change
916 * their current->fs->root to point to arbitrary
917 * directories. Since the intention of the "only dump
918 * with a fully qualified path" rule is to control where
919 * coredumps may be placed using root privileges,
920 * current->fs->root must not be used. Instead, use the
921 * root directory of init_task.
922 */
923 struct path root;
924
925 task_lock(p: &init_task);
926 get_fs_root(fs: init_task.fs, root: &root);
927 task_unlock(p: &init_task);
928 file = file_open_root(&root, cn->corename, open_flags, 0600);
929 path_put(&root);
930 } else {
931 file = filp_open(cn->corename, open_flags, 0600);
932 }
933 if (IS_ERR(ptr: file))
934 return false;
935
936 inode = file_inode(f: file);
937 if (inode->i_nlink > 1)
938 return false;
939 if (d_unhashed(dentry: file->f_path.dentry))
940 return false;
941 /*
942 * AK: actually i see no reason to not allow this for named
943 * pipes etc, but keep the previous behaviour for now.
944 */
945 if (!S_ISREG(inode->i_mode))
946 return false;
947 /*
948 * Don't dump core if the filesystem changed owner or mode
949 * of the file during file creation. This is an issue when
950 * a process dumps core while its cwd is e.g. on a vfat
951 * filesystem.
952 */
953 idmap = file_mnt_idmap(file);
954 if (!vfsuid_eq_kuid(vfsuid: i_uid_into_vfsuid(idmap, inode), current_fsuid())) {
955 coredump_report_failure("Core dump to %s aborted: cannot preserve file owner", cn->corename);
956 return false;
957 }
958 if ((inode->i_mode & 0677) != 0600) {
959 coredump_report_failure("Core dump to %s aborted: cannot preserve file permissions", cn->corename);
960 return false;
961 }
962 if (!(file->f_mode & FMODE_CAN_WRITE))
963 return false;
964 if (do_truncate(idmap, file->f_path.dentry, start: 0, time_attrs: 0, filp: file))
965 return false;
966
967 cprm->file = no_free_ptr(file);
968 return true;
969}
970
971static bool coredump_pipe(struct core_name *cn, struct coredump_params *cprm,
972 size_t *argv, int argc)
973{
974 int argi;
975 char **helper_argv __free(kfree) = NULL;
976 struct subprocess_info *sub_info;
977
978 if (cprm->limit == 1) {
979 /* See umh_coredump_setup() which sets RLIMIT_CORE = 1.
980 *
981 * Normally core limits are irrelevant to pipes, since
982 * we're not writing to the file system, but we use
983 * cprm.limit of 1 here as a special value, this is a
984 * consistent way to catch recursive crashes.
985 * We can still crash if the core_pattern binary sets
986 * RLIM_CORE = !1, but it runs as root, and can do
987 * lots of stupid things.
988 *
989 * Note that we use task_tgid_vnr here to grab the pid
990 * of the process group leader. That way we get the
991 * right pid if a thread in a multi-threaded
992 * core_pattern process dies.
993 */
994 coredump_report_failure("RLIMIT_CORE is set to 1, aborting core");
995 return false;
996 }
997 cprm->limit = RLIM_INFINITY;
998
999 cn->core_pipe_limit = atomic_inc_return(v: &core_pipe_count);
1000 if (core_pipe_limit && (core_pipe_limit < cn->core_pipe_limit)) {
1001 coredump_report_failure("over core_pipe_limit, skipping core dump");
1002 return false;
1003 }
1004
1005 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv), GFP_KERNEL);
1006 if (!helper_argv) {
1007 coredump_report_failure("%s failed to allocate memory", __func__);
1008 return false;
1009 }
1010 for (argi = 0; argi < argc; argi++)
1011 helper_argv[argi] = cn->corename + argv[argi];
1012 helper_argv[argi] = NULL;
1013
1014 sub_info = call_usermodehelper_setup(path: helper_argv[0], argv: helper_argv, NULL,
1015 GFP_KERNEL, init: umh_coredump_setup,
1016 NULL, data: cprm);
1017 if (!sub_info)
1018 return false;
1019
1020 if (call_usermodehelper_exec(info: sub_info, UMH_WAIT_EXEC)) {
1021 coredump_report_failure("|%s pipe failed", cn->corename);
1022 return false;
1023 }
1024
1025 /*
1026 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
1027 * have this set to NULL.
1028 */
1029 if (!cprm->file) {
1030 coredump_report_failure("Core dump to |%s disabled", cn->corename);
1031 return false;
1032 }
1033
1034 return true;
1035}
1036
1037static bool coredump_write(struct core_name *cn,
1038 struct coredump_params *cprm,
1039 struct linux_binfmt *binfmt)
1040{
1041
1042 if (dump_interrupted())
1043 return true;
1044
1045 if (!dump_vma_snapshot(cprm))
1046 return false;
1047
1048 file_start_write(file: cprm->file);
1049 cn->core_dumped = binfmt->core_dump(cprm);
1050 /*
1051 * Ensures that file size is big enough to contain the current
1052 * file postion. This prevents gdb from complaining about
1053 * a truncated file if the last "write" to the file was
1054 * dump_skip.
1055 */
1056 if (cprm->to_skip) {
1057 cprm->to_skip--;
1058 dump_emit(cprm, addr: "", nr: 1);
1059 }
1060 file_end_write(file: cprm->file);
1061 free_vma_snapshot(cprm);
1062 return true;
1063}
1064
1065static void coredump_cleanup(struct core_name *cn, struct coredump_params *cprm)
1066{
1067 if (cprm->file)
1068 filp_close(cprm->file, NULL);
1069 if (cn->core_pipe_limit) {
1070 VFS_WARN_ON_ONCE(cn->core_type != COREDUMP_PIPE);
1071 atomic_dec(v: &core_pipe_count);
1072 }
1073 kfree(objp: cn->corename);
1074 coredump_finish(core_dumped: cn->core_dumped);
1075}
1076
1077static inline bool coredump_skip(const struct coredump_params *cprm,
1078 const struct linux_binfmt *binfmt)
1079{
1080 if (!binfmt)
1081 return true;
1082 if (!binfmt->core_dump)
1083 return true;
1084 if (!__get_dumpable(mm_flags: cprm->mm_flags))
1085 return true;
1086 return false;
1087}
1088
1089void vfs_coredump(const kernel_siginfo_t *siginfo)
1090{
1091 struct cred *cred __free(put_cred) = NULL;
1092 size_t *argv __free(kfree) = NULL;
1093 struct core_state core_state;
1094 struct core_name cn;
1095 struct mm_struct *mm = current->mm;
1096 struct linux_binfmt *binfmt = mm->binfmt;
1097 const struct cred *old_cred;
1098 int argc = 0;
1099 struct coredump_params cprm = {
1100 .siginfo = siginfo,
1101 .limit = rlimit(RLIMIT_CORE),
1102 /*
1103 * We must use the same mm->flags while dumping core to avoid
1104 * inconsistency of bit flags, since this flag is not protected
1105 * by any locks.
1106 *
1107 * Note that we only care about MMF_DUMP* flags.
1108 */
1109 .mm_flags = __mm_flags_get_dumpable(mm),
1110 .vma_meta = NULL,
1111 .cpu = raw_smp_processor_id(),
1112 };
1113
1114 audit_core_dumps(signr: siginfo->si_signo);
1115
1116 if (coredump_skip(cprm: &cprm, binfmt))
1117 return;
1118
1119 cred = prepare_creds();
1120 if (!cred)
1121 return;
1122 /*
1123 * We cannot trust fsuid as being the "true" uid of the process
1124 * nor do we know its entire history. We only know it was tainted
1125 * so we dump it as root in mode 2, and only into a controlled
1126 * environment (pipe handler or fully qualified path).
1127 */
1128 if (coredump_force_suid_safe(cprm: &cprm))
1129 cred->fsuid = GLOBAL_ROOT_UID;
1130
1131 if (coredump_wait(siginfo->si_signo, &core_state) < 0)
1132 return;
1133
1134 old_cred = override_creds(cred);
1135
1136 if (!coredump_parse(&cn, &cprm, &argv, &argc)) {
1137 coredump_report_failure("format_corename failed, aborting core");
1138 goto close_fail;
1139 }
1140
1141 switch (cn.core_type) {
1142 case COREDUMP_FILE:
1143 if (!coredump_file(&cn, &cprm, binfmt))
1144 goto close_fail;
1145 break;
1146 case COREDUMP_PIPE:
1147 if (!coredump_pipe(&cn, &cprm, argv, argc))
1148 goto close_fail;
1149 break;
1150 case COREDUMP_SOCK_REQ:
1151 fallthrough;
1152 case COREDUMP_SOCK:
1153 if (!coredump_socket(&cn, &cprm))
1154 goto close_fail;
1155 break;
1156 default:
1157 WARN_ON_ONCE(true);
1158 goto close_fail;
1159 }
1160
1161 /* Don't even generate the coredump. */
1162 if (cn.mask & COREDUMP_REJECT)
1163 goto close_fail;
1164
1165 /* get us an unshared descriptor table; almost always a no-op */
1166 /* The cell spufs coredump code reads the file descriptor tables */
1167 if (unshare_files())
1168 goto close_fail;
1169
1170 if ((cn.mask & COREDUMP_KERNEL) && !coredump_write(&cn, &cprm, binfmt))
1171 goto close_fail;
1172
1173 coredump_sock_shutdown(cprm.file);
1174
1175 /* Let the parent know that a coredump was generated. */
1176 if (cn.mask & COREDUMP_USERSPACE)
1177 cn.core_dumped = true;
1178
1179 /*
1180 * When core_pipe_limit is set we wait for the coredump server
1181 * or usermodehelper to finish before exiting so it can e.g.,
1182 * inspect /proc/<pid>.
1183 */
1184 if (cn.mask & COREDUMP_WAIT) {
1185 switch (cn.core_type) {
1186 case COREDUMP_PIPE:
1187 wait_for_dump_helpers(cprm.file);
1188 break;
1189 case COREDUMP_SOCK_REQ:
1190 fallthrough;
1191 case COREDUMP_SOCK:
1192 coredump_sock_wait(cprm.file);
1193 break;
1194 default:
1195 break;
1196 }
1197 }
1198
1199close_fail:
1200 coredump_cleanup(&cn, &cprm);
1201 revert_creds(old_cred);
1202 return;
1203}
1204
1205/*
1206 * Core dumping helper functions. These are the only things you should
1207 * do on a core-file: use only these functions to write out all the
1208 * necessary info.
1209 */
1210static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
1211{
1212 struct file *file = cprm->file;
1213 loff_t pos = file->f_pos;
1214 ssize_t n;
1215
1216 if (cprm->written + nr > cprm->limit)
1217 return 0;
1218 if (dump_interrupted())
1219 return 0;
1220 n = __kernel_write(file, addr, nr, &pos);
1221 if (n != nr)
1222 return 0;
1223 file->f_pos = pos;
1224 cprm->written += n;
1225 cprm->pos += n;
1226
1227 return 1;
1228}
1229
1230static int __dump_skip(struct coredump_params *cprm, size_t nr)
1231{
1232 static char zeroes[PAGE_SIZE];
1233 struct file *file = cprm->file;
1234
1235 if (file->f_mode & FMODE_LSEEK) {
1236 if (dump_interrupted() || vfs_llseek(file, offset: nr, SEEK_CUR) < 0)
1237 return 0;
1238 cprm->pos += nr;
1239 return 1;
1240 }
1241
1242 while (nr > PAGE_SIZE) {
1243 if (!__dump_emit(cprm, addr: zeroes, PAGE_SIZE))
1244 return 0;
1245 nr -= PAGE_SIZE;
1246 }
1247
1248 return __dump_emit(cprm, addr: zeroes, nr);
1249}
1250
1251int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
1252{
1253 if (cprm->to_skip) {
1254 if (!__dump_skip(cprm, nr: cprm->to_skip))
1255 return 0;
1256 cprm->to_skip = 0;
1257 }
1258 return __dump_emit(cprm, addr, nr);
1259}
1260EXPORT_SYMBOL(dump_emit);
1261
1262void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
1263{
1264 cprm->to_skip = pos - cprm->pos;
1265}
1266EXPORT_SYMBOL(dump_skip_to);
1267
1268void dump_skip(struct coredump_params *cprm, size_t nr)
1269{
1270 cprm->to_skip += nr;
1271}
1272EXPORT_SYMBOL(dump_skip);
1273
1274#ifdef CONFIG_ELF_CORE
1275static int dump_emit_page(struct coredump_params *cprm, struct page *page)
1276{
1277 struct bio_vec bvec;
1278 struct iov_iter iter;
1279 struct file *file = cprm->file;
1280 loff_t pos;
1281 ssize_t n;
1282
1283 if (!page)
1284 return 0;
1285
1286 if (cprm->to_skip) {
1287 if (!__dump_skip(cprm, nr: cprm->to_skip))
1288 return 0;
1289 cprm->to_skip = 0;
1290 }
1291 if (cprm->written + PAGE_SIZE > cprm->limit)
1292 return 0;
1293 if (dump_interrupted())
1294 return 0;
1295 pos = file->f_pos;
1296 bvec_set_page(bv: &bvec, page, PAGE_SIZE, offset: 0);
1297 iov_iter_bvec(i: &iter, ITER_SOURCE, bvec: &bvec, nr_segs: 1, PAGE_SIZE);
1298 n = __kernel_write_iter(file: cprm->file, from: &iter, pos: &pos);
1299 if (n != PAGE_SIZE)
1300 return 0;
1301 file->f_pos = pos;
1302 cprm->written += PAGE_SIZE;
1303 cprm->pos += PAGE_SIZE;
1304
1305 return 1;
1306}
1307
1308/*
1309 * If we might get machine checks from kernel accesses during the
1310 * core dump, let's get those errors early rather than during the
1311 * IO. This is not performance-critical enough to warrant having
1312 * all the machine check logic in the iovec paths.
1313 */
1314#ifdef copy_mc_to_kernel
1315
1316#define dump_page_alloc() alloc_page(GFP_KERNEL)
1317#define dump_page_free(x) __free_page(x)
1318static struct page *dump_page_copy(struct page *src, struct page *dst)
1319{
1320 void *buf = kmap_local_page(page: src);
1321 size_t left = copy_mc_to_kernel(page_address(dst), from: buf, PAGE_SIZE);
1322 kunmap_local(buf);
1323 return left ? NULL : dst;
1324}
1325
1326#else
1327
1328/* We just want to return non-NULL; it's never used. */
1329#define dump_page_alloc() ERR_PTR(-EINVAL)
1330#define dump_page_free(x) ((void)(x))
1331static inline struct page *dump_page_copy(struct page *src, struct page *dst)
1332{
1333 return src;
1334}
1335#endif
1336
1337int dump_user_range(struct coredump_params *cprm, unsigned long start,
1338 unsigned long len)
1339{
1340 unsigned long addr;
1341 struct page *dump_page;
1342 int locked, ret;
1343
1344 dump_page = dump_page_alloc();
1345 if (!dump_page)
1346 return 0;
1347
1348 ret = 0;
1349 locked = 0;
1350 for (addr = start; addr < start + len; addr += PAGE_SIZE) {
1351 struct page *page;
1352
1353 if (!locked) {
1354 if (mmap_read_lock_killable(current->mm))
1355 goto out;
1356 locked = 1;
1357 }
1358
1359 /*
1360 * To avoid having to allocate page tables for virtual address
1361 * ranges that have never been used yet, and also to make it
1362 * easy to generate sparse core files, use a helper that returns
1363 * NULL when encountering an empty page table entry that would
1364 * otherwise have been filled with the zero page.
1365 */
1366 page = get_dump_page(addr, locked: &locked);
1367 if (page) {
1368 if (locked) {
1369 mmap_read_unlock(current->mm);
1370 locked = 0;
1371 }
1372 int stop = !dump_emit_page(cprm, page: dump_page_copy(src: page, dst: dump_page));
1373 put_page(page);
1374 if (stop)
1375 goto out;
1376 } else {
1377 dump_skip(cprm, PAGE_SIZE);
1378 }
1379
1380 if (dump_interrupted())
1381 goto out;
1382
1383 if (!need_resched())
1384 continue;
1385 if (locked) {
1386 mmap_read_unlock(current->mm);
1387 locked = 0;
1388 }
1389 cond_resched();
1390 }
1391 ret = 1;
1392out:
1393 if (locked)
1394 mmap_read_unlock(current->mm);
1395
1396 dump_page_free(dump_page);
1397 return ret;
1398}
1399#endif
1400
1401int dump_align(struct coredump_params *cprm, int align)
1402{
1403 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
1404 if (align & (align - 1))
1405 return 0;
1406 if (mod)
1407 cprm->to_skip += align - mod;
1408 return 1;
1409}
1410EXPORT_SYMBOL(dump_align);
1411
1412#ifdef CONFIG_SYSCTL
1413
1414void validate_coredump_safety(void)
1415{
1416 if (suid_dumpable == SUID_DUMP_ROOT &&
1417 core_pattern[0] != '/' && core_pattern[0] != '|' && core_pattern[0] != '@') {
1418
1419 coredump_report_failure("Unsafe core_pattern used with fs.suid_dumpable=2: "
1420 "pipe handler or fully qualified core dump path required. "
1421 "Set kernel.core_pattern before fs.suid_dumpable.");
1422 }
1423}
1424
1425static inline bool check_coredump_socket(void)
1426{
1427 const char *p;
1428
1429 if (core_pattern[0] != '@')
1430 return true;
1431
1432 /*
1433 * Coredump socket must be located in the initial mount
1434 * namespace. Don't give the impression that anything else is
1435 * supported right now.
1436 */
1437 if (current->nsproxy->mnt_ns != init_task.nsproxy->mnt_ns)
1438 return false;
1439
1440 /* Must be an absolute path... */
1441 if (core_pattern[1] != '/') {
1442 /* ... or the socket request protocol... */
1443 if (core_pattern[1] != '@')
1444 return false;
1445 /* ... and if so must be an absolute path. */
1446 if (core_pattern[2] != '/')
1447 return false;
1448 p = &core_pattern[2];
1449 } else {
1450 p = &core_pattern[1];
1451 }
1452
1453 /* The path obviously cannot exceed UNIX_PATH_MAX. */
1454 if (strlen(p) >= UNIX_PATH_MAX)
1455 return false;
1456
1457 /* Must not contain ".." in the path. */
1458 if (name_contains_dotdot(name: core_pattern))
1459 return false;
1460
1461 return true;
1462}
1463
1464static int proc_dostring_coredump(const struct ctl_table *table, int write,
1465 void *buffer, size_t *lenp, loff_t *ppos)
1466{
1467 int error;
1468 ssize_t retval;
1469 char old_core_pattern[CORENAME_MAX_SIZE];
1470
1471 if (write)
1472 return proc_dostring(table, write, buffer, lenp, ppos);
1473
1474 retval = strscpy(old_core_pattern, core_pattern, CORENAME_MAX_SIZE);
1475
1476 error = proc_dostring(table, write, buffer, lenp, ppos);
1477 if (error)
1478 return error;
1479
1480 if (!check_coredump_socket()) {
1481 strscpy(core_pattern, old_core_pattern, retval + 1);
1482 return -EINVAL;
1483 }
1484
1485 validate_coredump_safety();
1486 return error;
1487}
1488
1489static const unsigned int core_file_note_size_min = CORE_FILE_NOTE_SIZE_DEFAULT;
1490static const unsigned int core_file_note_size_max = CORE_FILE_NOTE_SIZE_MAX;
1491static char core_modes[] = {
1492 "file\npipe"
1493#ifdef CONFIG_UNIX
1494 "\nsocket"
1495#endif
1496};
1497
1498static const struct ctl_table coredump_sysctls[] = {
1499 {
1500 .procname = "core_uses_pid",
1501 .data = &core_uses_pid,
1502 .maxlen = sizeof(int),
1503 .mode = 0644,
1504 .proc_handler = proc_dointvec,
1505 },
1506 {
1507 .procname = "core_pattern",
1508 .data = core_pattern,
1509 .maxlen = CORENAME_MAX_SIZE,
1510 .mode = 0644,
1511 .proc_handler = proc_dostring_coredump,
1512 },
1513 {
1514 .procname = "core_pipe_limit",
1515 .data = &core_pipe_limit,
1516 .maxlen = sizeof(unsigned int),
1517 .mode = 0644,
1518 .proc_handler = proc_dointvec_minmax,
1519 .extra1 = SYSCTL_ZERO,
1520 .extra2 = SYSCTL_INT_MAX,
1521 },
1522 {
1523 .procname = "core_file_note_size_limit",
1524 .data = &core_file_note_size_limit,
1525 .maxlen = sizeof(unsigned int),
1526 .mode = 0644,
1527 .proc_handler = proc_douintvec_minmax,
1528 .extra1 = (unsigned int *)&core_file_note_size_min,
1529 .extra2 = (unsigned int *)&core_file_note_size_max,
1530 },
1531 {
1532 .procname = "core_sort_vma",
1533 .data = &core_sort_vma,
1534 .maxlen = sizeof(int),
1535 .mode = 0644,
1536 .proc_handler = proc_douintvec_minmax,
1537 .extra1 = SYSCTL_ZERO,
1538 .extra2 = SYSCTL_ONE,
1539 },
1540 {
1541 .procname = "core_modes",
1542 .data = core_modes,
1543 .maxlen = sizeof(core_modes) - 1,
1544 .mode = 0444,
1545 .proc_handler = proc_dostring,
1546 },
1547};
1548
1549static int __init init_fs_coredump_sysctls(void)
1550{
1551 register_sysctl_init("kernel", coredump_sysctls);
1552 return 0;
1553}
1554fs_initcall(init_fs_coredump_sysctls);
1555#endif /* CONFIG_SYSCTL */
1556
1557/*
1558 * The purpose of always_dump_vma() is to make sure that special kernel mappings
1559 * that are useful for post-mortem analysis are included in every core dump.
1560 * In that way we ensure that the core dump is fully interpretable later
1561 * without matching up the same kernel and hardware config to see what PC values
1562 * meant. These special mappings include - vDSO, vsyscall, and other
1563 * architecture specific mappings
1564 */
1565static bool always_dump_vma(struct vm_area_struct *vma)
1566{
1567 /* Any vsyscall mappings? */
1568 if (vma == get_gate_vma(mm: vma->vm_mm))
1569 return true;
1570
1571 /*
1572 * Assume that all vmas with a .name op should always be dumped.
1573 * If this changes, a new vm_ops field can easily be added.
1574 */
1575 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
1576 return true;
1577
1578 /*
1579 * arch_vma_name() returns non-NULL for special architecture mappings,
1580 * such as vDSO sections.
1581 */
1582 if (arch_vma_name(vma))
1583 return true;
1584
1585 return false;
1586}
1587
1588#define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
1589
1590/*
1591 * Decide how much of @vma's contents should be included in a core dump.
1592 */
1593static unsigned long vma_dump_size(struct vm_area_struct *vma,
1594 unsigned long mm_flags)
1595{
1596#define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
1597
1598 /* always dump the vdso and vsyscall sections */
1599 if (always_dump_vma(vma))
1600 goto whole;
1601
1602 if (vma->vm_flags & VM_DONTDUMP)
1603 return 0;
1604
1605 /* support for DAX */
1606 if (vma_is_dax(vma)) {
1607 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1608 goto whole;
1609 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1610 goto whole;
1611 return 0;
1612 }
1613
1614 /* Hugetlb memory check */
1615 if (is_vm_hugetlb_page(vma)) {
1616 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1617 goto whole;
1618 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1619 goto whole;
1620 return 0;
1621 }
1622
1623 /* Do not dump I/O mapped devices or special mappings */
1624 if (vma->vm_flags & VM_IO)
1625 return 0;
1626
1627 /* By default, dump shared memory if mapped from an anonymous file. */
1628 if (vma->vm_flags & VM_SHARED) {
1629 if (file_inode(f: vma->vm_file)->i_nlink == 0 ?
1630 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1631 goto whole;
1632 return 0;
1633 }
1634
1635 /* Dump segments that have been written to. */
1636 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1637 goto whole;
1638 if (vma->vm_file == NULL)
1639 return 0;
1640
1641 if (FILTER(MAPPED_PRIVATE))
1642 goto whole;
1643
1644 /*
1645 * If this is the beginning of an executable file mapping,
1646 * dump the first page to aid in determining what was mapped here.
1647 */
1648 if (FILTER(ELF_HEADERS) &&
1649 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1650 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1651 return PAGE_SIZE;
1652
1653 /*
1654 * ELF libraries aren't always executable.
1655 * We'll want to check whether the mapping starts with the ELF
1656 * magic, but not now - we're holding the mmap lock,
1657 * so copy_from_user() doesn't work here.
1658 * Use a placeholder instead, and fix it up later in
1659 * dump_vma_snapshot().
1660 */
1661 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1662 }
1663
1664#undef FILTER
1665
1666 return 0;
1667
1668whole:
1669 return vma->vm_end - vma->vm_start;
1670}
1671
1672/*
1673 * Helper function for iterating across a vma list. It ensures that the caller
1674 * will visit `gate_vma' prior to terminating the search.
1675 */
1676static struct vm_area_struct *coredump_next_vma(struct vma_iterator *vmi,
1677 struct vm_area_struct *vma,
1678 struct vm_area_struct *gate_vma)
1679{
1680 if (gate_vma && (vma == gate_vma))
1681 return NULL;
1682
1683 vma = vma_next(vmi);
1684 if (vma)
1685 return vma;
1686 return gate_vma;
1687}
1688
1689static void free_vma_snapshot(struct coredump_params *cprm)
1690{
1691 if (cprm->vma_meta) {
1692 int i;
1693 for (i = 0; i < cprm->vma_count; i++) {
1694 struct file *file = cprm->vma_meta[i].file;
1695 if (file)
1696 fput(file);
1697 }
1698 kvfree(addr: cprm->vma_meta);
1699 cprm->vma_meta = NULL;
1700 }
1701}
1702
1703static int cmp_vma_size(const void *vma_meta_lhs_ptr, const void *vma_meta_rhs_ptr)
1704{
1705 const struct core_vma_metadata *vma_meta_lhs = vma_meta_lhs_ptr;
1706 const struct core_vma_metadata *vma_meta_rhs = vma_meta_rhs_ptr;
1707
1708 if (vma_meta_lhs->dump_size < vma_meta_rhs->dump_size)
1709 return -1;
1710 if (vma_meta_lhs->dump_size > vma_meta_rhs->dump_size)
1711 return 1;
1712 return 0;
1713}
1714
1715/*
1716 * Under the mmap_lock, take a snapshot of relevant information about the task's
1717 * VMAs.
1718 */
1719static bool dump_vma_snapshot(struct coredump_params *cprm)
1720{
1721 struct vm_area_struct *gate_vma, *vma = NULL;
1722 struct mm_struct *mm = current->mm;
1723 VMA_ITERATOR(vmi, mm, 0);
1724 int i = 0;
1725
1726 /*
1727 * Once the stack expansion code is fixed to not change VMA bounds
1728 * under mmap_lock in read mode, this can be changed to take the
1729 * mmap_lock in read mode.
1730 */
1731 if (mmap_write_lock_killable(mm))
1732 return false;
1733
1734 cprm->vma_data_size = 0;
1735 gate_vma = get_gate_vma(mm);
1736 cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1737
1738 cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1739 if (!cprm->vma_meta) {
1740 mmap_write_unlock(mm);
1741 return false;
1742 }
1743
1744 while ((vma = coredump_next_vma(vmi: &vmi, vma, gate_vma)) != NULL) {
1745 struct core_vma_metadata *m = cprm->vma_meta + i;
1746
1747 m->start = vma->vm_start;
1748 m->end = vma->vm_end;
1749 m->flags = vma->vm_flags;
1750 m->dump_size = vma_dump_size(vma, mm_flags: cprm->mm_flags);
1751 m->pgoff = vma->vm_pgoff;
1752 m->file = vma->vm_file;
1753 if (m->file)
1754 get_file(f: m->file);
1755 i++;
1756 }
1757
1758 mmap_write_unlock(mm);
1759
1760 for (i = 0; i < cprm->vma_count; i++) {
1761 struct core_vma_metadata *m = cprm->vma_meta + i;
1762
1763 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1764 char elfmag[SELFMAG];
1765
1766 if (copy_from_user(to: elfmag, from: (void __user *)m->start, SELFMAG) ||
1767 memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1768 m->dump_size = 0;
1769 } else {
1770 m->dump_size = PAGE_SIZE;
1771 }
1772 }
1773
1774 cprm->vma_data_size += m->dump_size;
1775 }
1776
1777 if (core_sort_vma)
1778 sort(base: cprm->vma_meta, num: cprm->vma_count, size: sizeof(*cprm->vma_meta),
1779 cmp_func: cmp_vma_size, NULL);
1780
1781 return true;
1782}
1783